This invention relates to an intake control device for a multi-cylinder, v-type, internal combustion engine and more particularly to an improved tuned type intake system for such an engine.
It has been acknowledged that the performance of an internal combustion engine can be improved over a wide range of speed and load conditions by utilizing what is referred to as a xe2x80x9cvariable tunedxe2x80x9d intake system. Such intake systems have the capability of providing different effective lengths for the intake runners so as to improve charging efficiency under varying running conditions. For example, it is known that for good low speed charging efficiency, the intake path should be long while to improve charging efficiency under high speed high load conditions, it should be very short. A number of types of arrangements have been proposed for providing this type of result.
Once such arrangement is shown in U.S. Pat. No. 5,787,851, issued Aug. 4, 1998 and entitled xe2x80x9cIntake Control Systemxe2x80x9d, which patent is assigned to the assignee hereof. In that arrangement, there is provided a plenum chamber into which the intake tracts for each cylinder of the engine extend, at least in part. The intake tracts have two separate openings into the plenum chamber, one of which is valved. Generally this is the shorter intake path and its opening is closed under low and mid range running conditions. By opening the valve at higher speed conditions, the effective length of the intake passage is shortened and it is tuned for better high speed, high load performance.
As shown in that patent, the induction system is described in conjunction with a V-type engine wherein the plenum chamber extends through the valley of the V configuration between the cylinder banks. The inlet openings of both of the long and short parts of the passages extend in a direction facing toward the valley. This means that the intake charge must change direction to flow into the intake tract for each cylinder. This change in flow direction creates a restriction to flow which, particularly under high speed high load conditions, can deteriorate the performance from that desired.
It is, therefore, a principal object to this invention to provide an improved variable tuned intake system for a V-type engine wherein at least one of the intake passages extends in a direction away from the valley and thus, permits a more direct flow to the intake system to improve performance.
In accordance with a principal feature of the invention, this outwardly facing passage constitutes the high speed path although in the preferred embodiment, both the high and low speed paths face in this direction.
This invention is adapted to be embodied in a V-type, multi-cylinder internal combustion engine comprised of a cylinder head, cylinder block arrangement that consists of a pair of angularly disposed cylinder banks with their intake ports disposed adjacent a valley defined between the cylinder banks. An induction is provided for delivering at least an air charge to the intake ports. The induction system is comprised of a surge tank disposed in substantial part in the valley and having an air inlet through which an air charge is delivered to the interior of the surge tank. A plurality of curvilinear intake pipes, each extend from a respective one of the intake ports into the surge tank. Each of the curvilinear intake pipes have a low speed inlet opening in the surge tank at the end remote from the served intake port and a valved high speed inlet opening into the surge tank spaced a lesser distance from the served intake port to provide a substantially lesser flow length from the surge tank to the served intake port when the valved high speed inlet opening is opened. At least the valved high speed inlet opening faces away from the valley into the surge tank.